Actually, thinking about this, I may have defined the ramp in incorrectly. It would be interesting to see what Code Sheetcam generates for wiggle and ramp in.

I also think that as Stefan said, you don't need to worry about this on thin material and you probably are not going to be able to find it useful with a 45 amp machine.

Looking at my 120 amp machine, the pierce time at 16mm thick mild steel is 0.7 seconds but that becomes 1.6 seconds at 20mm.
The same machine at 40 amps, 12mm quotes pierce delay of 2 seconds so we are piercing faster than a smaller machine.

The book say edge start should be used for thicknesses from 25mm to 40mm so its probably in that range that the ramp in would become useful. I have not cut anything thicker than 16mm. The torch has nearly pierced it before it gets an ArcOK!

I kinda think if you were going to do this in the controller (eg. Plasmac), perhaps the controller would offset the start point so that the ramp in was at the programmed start point on completion of the pierce. This is a level of sophistication well beyond where we currently are and I think perhaps is something that could be easier in a plasmatask module suggested by Andy. I discussed this yesterday in another thread. I have got as far as compiling a copy of milltask renamed as plasmatask as proof of concept and I got that working in about half an hour but I suspect real modifications might take a bit longer!

Just to be clear when talking about piercing being controlled by the controller, I am not talking about a simple Gcode filter but doing it internally either within HAL via a component or deeper in Linuxcnc's internals via a modified version of task.

I agree it's probably not something I would really need with a small machine. Probably most hobby users wouldn't but there might be a few and I suspect some of the "business" users out there could see some benefit - Grotius certainly comes to mind. It would bring plasmac closer to what some of the more expensive software is (apparently) doing.

That would definitely be on a different level to do this with a new plasmatask module. I have not gotten into the internal workings of LinuxCNC enough to even do a competent thought experiment on that.

I did look at "wiggle pierce" and "ramp pierce" some time ago but I seem to recall Jim Colt mentioning something along the lines of HT recommending against it as their torches are designed for stationary piercing and also that having motion while piercing increase the amount of molten material blowing back in unknown directions. Which kind makes sense to me.
I wish I could find where I saw that post but I can't at the moment. Anyhow it convinced to not go in that direction.

A wiggle would be pretty easy to achieve in hal. You could create a sine wave using siggen and apply it to the Z (or Y) axis external offset either for a specific time delay or for the duration of the pierce delay. This could be achieved outside of plasmac.

I gotta think about the other one (ramp).

I had a look at a ramp pierce in Sheetcam but could not see anything obvious had changed in the gcode.

phillc54 wrote: I did look at "wiggle pierce" and "ramp pierce" some time ago but I seem to recall Jim Colt mentioning something along the lines of HT recommending against it as their torches are designed for stationary piercing and also that having motion while piercing increase the amount of molten material blowing back in unknown directions.

That sums up my experience as well. Piercing thick plate (20-25mm) at the best of times produces molten metal spray in all kinds of directions, Adding motion to it would in my opinion make the situation much worse.

I have been having problems with 20mm plate spraying molten metal from piercing holes over the external cuts area of parts, When the torch is cutting the external part at cut height it hits the molten metal and causes a fault. I am not exactly sure how to deal with this yet but at least the molten metal is in the same spot every time. Making the spray unpredictable would in my experience make the situation much worse.

The book Hyperthem setting have worked well for me piercing metals from 1.6mm up to 25mm.

I don't think Sheetcam supports it so I filed that in the useless ideas bin

But maybe if you disabled the torch straight after a pierce, you could let it run the job twice. eg.
If we create another custom tool (like my centrepunch tool) in sheetcam for "Pierce Only" that issues a M62 P3 straight after the pierce delay (eg straight after M3 in Plasmac), you might be able to get away with that. Just run a second operation with a normal cut but no pierce delay.